import { createReducer } from '@reduxjs/toolkit'

import {
  acceptListUpdate,
  addList,
  fetchTokenList,
  removeList,
  enableList,
  disableList,
  updateListVersion,
} from './actions'
import { getVersionUpgrade, VersionUpgrade, TokenList } from '../src'

export interface ListsState {
  readonly byUrl: {
    readonly [url: string]: {
      readonly current: TokenList | null
      readonly pendingUpdate: TokenList | null
      readonly loadingRequestId: string | null
      readonly error: string | null
    }
  }
  // this contains the default list of lists from the last time the updateVersion was called, i.e. the app was reloaded
  readonly lastInitializedDefaultListOfLists?: string[]

  // currently active lists
  readonly activeListUrls: string[] | undefined
}

export type ListByUrlState = ListsState['byUrl'][string]

export const NEW_LIST_STATE: ListByUrlState = {
  error: null,
  current: null,
  loadingRequestId: null,
  pendingUpdate: null,
}

export const createTokenListReducer = (
  initialState: ListsState,
  DEFAULT_LIST_OF_LISTS: string[],
  DEFAULT_ACTIVE_LIST_URLS: string[],
) =>
  createReducer(initialState, (builder) =>
    builder
      .addCase(fetchTokenList.pending, (state, { payload: { requestId, url } }) => {
        const current = state.byUrl[url]?.current ?? null
        const pendingUpdate = state.byUrl[url]?.pendingUpdate ?? null

        state.byUrl[url] = {
          current,
          pendingUpdate,
          loadingRequestId: requestId,
          error: null,
        }
      })
      .addCase(fetchTokenList.fulfilled, (state, { payload: { requestId, tokenList, url } }) => {
        const current = state.byUrl[url]?.current
        const loadingRequestId = state.byUrl[url]?.loadingRequestId

        // no-op if update does nothing
        if (current) {
          const upgradeType = getVersionUpgrade(current.version, tokenList.version)

          if (upgradeType === VersionUpgrade.NONE) return
          if (loadingRequestId === null || loadingRequestId === requestId) {
            state.byUrl[url] = {
              ...state.byUrl[url],
              loadingRequestId: null,
              error: null,
              current,
              pendingUpdate: tokenList,
            }
          }
        } else {
          // activate if on default active
          if (DEFAULT_ACTIVE_LIST_URLS.includes(url) && state.activeListUrls && !state.activeListUrls.includes(url)) {
            state.activeListUrls.push(url)
          }

          state.byUrl[url] = {
            ...state.byUrl[url],
            loadingRequestId: null,
            error: null,
            current: tokenList,
            pendingUpdate: null,
          }
        }
      })
      .addCase(fetchTokenList.rejected, (state, { payload: { url, requestId, errorMessage } }) => {
        if (state.byUrl[url]?.loadingRequestId !== requestId) {
          // no-op since it's not the latest request
          return
        }

        state.byUrl[url] = {
          ...state.byUrl[url],
          loadingRequestId: null,
          error: errorMessage,
          current: null,
          pendingUpdate: null,
        }
      })
      .addCase(addList, (state, { payload: url }) => {
        if (!state.byUrl[url]) {
          state.byUrl[url] = NEW_LIST_STATE
        }
      })
      .addCase(removeList, (state, { payload: url }) => {
        if (state.byUrl[url]) {
          delete state.byUrl[url]
        }
        // remove list from active urls if needed
        if (state.activeListUrls && state.activeListUrls.includes(url)) {
          state.activeListUrls = state.activeListUrls.filter((u) => u !== url)
        }
      })
      .addCase(enableList, (state, { payload: url }) => {
        if (!state.byUrl[url]) {
          state.byUrl[url] = NEW_LIST_STATE
        }

        if (state.activeListUrls && !state.activeListUrls.includes(url)) {
          state.activeListUrls.push(url)
        }

        if (!state.activeListUrls) {
          state.activeListUrls = [url]
        }
      })
      .addCase(disableList, (state, { payload: url }) => {
        if (state.activeListUrls && state.activeListUrls.includes(url)) {
          state.activeListUrls = state.activeListUrls.filter((u) => u !== url)
        }
      })
      .addCase(acceptListUpdate, (state, { payload: url }) => {
        if (!state.byUrl[url]?.pendingUpdate) {
          throw new Error('accept list update called without pending update')
        }
        state.byUrl[url] = {
          ...state.byUrl[url],
          pendingUpdate: null,
          current: state.byUrl[url].pendingUpdate,
        }
      })
      .addCase(updateListVersion, (state) => {
        // state loaded from localStorage, but new lists have never been initialized
        if (!state.lastInitializedDefaultListOfLists) {
          state.byUrl = initialState.byUrl
          state.activeListUrls = initialState.activeListUrls
        } else if (state.lastInitializedDefaultListOfLists) {
          const lastInitializedSet = state.lastInitializedDefaultListOfLists.reduce<Set<string>>(
            (s, l) => s.add(l),
            new Set(),
          )
          const newListOfListsSet = DEFAULT_LIST_OF_LISTS.reduce<Set<string>>((s, l) => s.add(l), new Set())

          DEFAULT_LIST_OF_LISTS.forEach((listUrl) => {
            if (!lastInitializedSet.has(listUrl)) {
              state.byUrl[listUrl] = NEW_LIST_STATE
            }
          })

          state.lastInitializedDefaultListOfLists.forEach((listUrl) => {
            if (!newListOfListsSet.has(listUrl)) {
              delete state.byUrl[listUrl]
            }
          })
        }

        state.lastInitializedDefaultListOfLists = DEFAULT_LIST_OF_LISTS

        // if no active lists, activate defaults
        if (!state.activeListUrls) {
          state.activeListUrls = DEFAULT_ACTIVE_LIST_URLS

          // for each list on default list, initialize if needed
          DEFAULT_ACTIVE_LIST_URLS.forEach((listUrl: string) => {
            if (!state.byUrl[listUrl]) {
              state.byUrl[listUrl] = NEW_LIST_STATE
            }
            return true
          })
        }
      }),
  )